I. Field of the Invention
This invention relates generally to hand tools used by carpet installers, and more particularly to an improved tool for creating a clean straight cut through the thickness dimension of foam back carpeting so that a smooth unnoticeable seam results where two pieces of the carpet material are brought into edge wise abutment.
II. Discussion of the Prior Art
The Scott et al. U.S. Pat. No. 3,543,401 describes a cushion back carpet cutter that has left-hand and right-hand blades for selectively cutting close to tufted piles on the left and right sides of the spaces between adjacent rows of tufts. It comprises a guide having a longitudinal edge for engaging the top surface of carpet backing between adjacent rows of tufts and a leading edge that meets the longitudinally extending edge at an angle of 90xc2x0. The guide plate is sandwiched between two retaining plates and a handle is attached to the retaining plates at an upper edge thereof to facilitate grasping of the tool during use.
Formed inwardly of the longitudinal edge of the guide plate is an inclined blade notch that is disposed at an acute angle of about 30xc2x0 to the longitudinal edge of the guide plate. A pair of rectangular blades, each with a razor-sharp honed edge, is disposed within the blade notch in the guide plate in side-by-side relation, allowing either the left or the right blade to be extended relative to the longitudinal edge of the guide plate and then clamped by a thumb screw and nut to hold their position within the blade notch.
While the cutter made in accordance with the Scott et al. patent works satisfactorily with some cushion back carpet materials, it has been found that it suffers from a number of draw-backs when attempts are made to use it with newer polyurethane backed carpet materials. A 30xc2x0 blade angle has been found to create frayed, jagged edges on the polyurethane layer that makes it difficult for an installer to bring two edges into contact without seeing a noticeable line at the seam. Also, when using the prior-art Scott et al. carpet cutting tool, it is first necessary to use a separate, row-opening tool to provide a space for entry of the cutting tool""s guide plate. Further, the relatively large radius of the nose frequently results in the tool jumping out of a row as the operator attempts to push the tool along that row. Then, too, the 90xc2x0 angle between the leading edge of the guide plate and the longitudinal, carpet-engaging edge resulted in frequent catching and snagging when attempting to cut through either loop pile carpeting or woven carpeting.
In accordance with the present invention, several modifications have been made to the tool of the Scott et al. patent to obviate its shortcomings. Specifically, in accordance with the present invention, the blade notch is at a much shallower angle with respect to the longitudinal edge of the tool""s guide plate. Instead of a 30xc2x0 angle as in the Scott et al. device, in the present invention, the angle is between 15xc2x0-25xc2x0. This shallower angle results in a much smoother cut edge, even with lightweight polyurethane back carpets. Moreover, by decreasing the angle of inclination of the cutting blade slot, less force on the handle is required to advance the cutting tool through the backing material, reducing operator effort.
Furthermore, in accordance with the present invention, there is provided a three-blade cavity or blade notch allowing an operator to cut to the right, cut to the left or cut dead center in the row between adjacent tufts.
We have also determined that by slightly altering the 90xc2x0 angle between the leading edge of the guide plate and its longitudinal, carpet engaging edge, such as by having an angle in a range of from 80xc2x0-86xc2x0 and with a smaller radius at the edge intersection, the improved cutter of the present invention does not catch on loop carpeting or on woven carpeting, nor does it jump out of the row where the cut is being made.